The invention relates to a method and an apparatus for determining the composition of free-flowing or fluidizable solid matter particles, which may be for instance powdery or granular, in particular for determining the composition of a color powder. The invention in particular relates to the determination of the composition of a coating powder for an electrostatic powder coating apparatus with respect to its average particle size and physical and/or chemical properties.
With the increasing quality demands of powder coating technology the demands on quality of the coating powder to be processed also rise continuously. Modern powder coating apparatus and devices may be adjusted precisely to the coating powder to be sprayed in order to reach an optimum coating quality. In order to ensure a constant quality, it is necessary to maintain a quality level achieved by a certain adjustment without interruption over a long period of time.
The supply means and coating devices are developed continually and permit more specific adjustments, for instance an adjustment of the powder supply so that with a certain powder quality a predetermined or maximum flow rate at an optimum electrostatic charging of the coating powder is achieved. The powder quality is reflected for instance by the average particle size, the grain size distribution and/or the chemical properties of the powder. Since the supply means and coating devices are precisely adjusted to the respective powder quality, fluctuations in quality of the coating powder have a very strong influence on the final coating quality. Quality fluctuations of that kind in particular occur when a new powder batch is used.
The methods of the prior art of inspecting the coating powder take a relatively long time and involve expensive chemical analysis and/or physical tests, e.g. for determining the particle size distribution of the powder. In order to ensure a constant coating quality, these tests would always have to be conducted before use of a new powder batch, which is not practical for time and cost reasons.